Description:

Title: The role of long-range strain interactions in perovskite metal-insulator transitions

Speaker: Dr. Richard Brierley, Yale University

Abstract: Metal-insulator transitions in manganite and nickelate perovskites depend on the competition between the electron kinetic energy, which favors the metallic phase, and the electron-phonon coupling and Coulomb interaction, which favor localization. The perovskite crystal structure consists of corner-sharing octahedra, which, depending on the chemical composition, can be tilted relative to each other by up to 15 degrees. This is accompanied by changes in the metal-insulator transition temperature over 600K. The significant change in transition temperature is commonly attributed to electronic effects but this relies ignores phonons, which are known to play an important role in the transition. We study how phonon-mediated long-range interactions are changed by the octahedral tilting. Using a simple statistical mechanical model we demonstrate that these changes can lead to variations in the transition temperature similar to those observed in both the manganites and nickelates.

Keywords: Physics, Astronomy, CMP